Coating composition comprising a bicyclo- or spiro-orthoester functional compound

A polymer comprising at least one bicyclo-orthoester group according to formula I

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• wherein
• X and Z are independently from each other selected from linear and branched alk(en)ylene groups with 1-4 carbon atoms optionally containing an oxygen or a nitrogen atom;
• Y is nothing or is selected independently of X and Z from linear and branched alk(en)ylene groups with 1-4 carbon atoms optionally containing an oxygen or a nitrogen atom;
• one of R1 and R2 is a monovalent radical and the other is a divalent radical or both groups are independently from each other selected from the group of divalent radicals,
• the monovalent radicals comprising
• hydrogen, hydroxyl, alk(en)yl groups comprising 1-30 carbon atoms which may be linear or branched and may optionally contain one or more heteroatoms and groups selected from the group of oxygen, nitrogen, sulphur, phosphorus, sulphone, sulphoxy, and ester, optionally substituted with epoxy, cyano, amino, thiol, hydroxyl, halogen, nitro, phosphorus, sulphoxy, amido, ether, ester, urea, urethane, thioester, thioamide, amide, carboxyl, carbonyl, aryl, and acyl groups, and
• divalent radicals comprising
• alk(en)ylene groups having 1-10 carbon atoms which groups may be linear or branched and may optionally contain one or more heteroatoms and groups selected from the group of oxygen, nitrogen, sulphur, phosphorus, sulphone, sulphoxy, and ester, optionally substituted with epoxy, cyano, amino, thiol, hydroxyl, halogen, nitro, phosphorus, sulphoxy, amido, ether, ester, urea, urethane, thioester, thioamide, amide, carboxyl, carbonyl, aryl, and acyl groups, ester groups;
• ether groups;
• amide groups;
• thioester groups;
• thioamide groups;
• urethane groups;
• urea groups;
• and a single bond.

A polymer comprising at least one spiro-orthoester group according to formula II or III

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• wherein
• R3 and R5 are independently from each other selected from the group of linear or branched alk(en)yl, aryl or acyl optionally containing one or more oxygen, nitrogen, sulphur or phosphorus atoms, optionally substituted with a halogen atom;
• and
• R4 and R6 are independently from each other selected from an alkylene group having 1-3 carbon atoms optionally substituted with one or more groups selected from monovalent radicals such as linear or branched alk(en)yl, aryl or acyl groups optionally containing one or more oxygen, nitrogen, sulphur, and phosphorus atoms;
• and at least once substituted with a divalent radical selected from the group of a single bond and an alkylene group having 1-10 carbon atoms with or without one or more atoms and groups selected from oxygen, nitrogen, sulphur, and phosphorus atoms, and ether, ester, and urethane groups.